The invention relates to a rotor with permanent magnets for an electrical machine.
It is known to provide a rotor with tangentially oriented permanent magnets and pole pieces arranged between them. The magnets are radially secured by means of non-magnetic cotters driven into grooves provided in the upper part of the lateral surfaces of the pole pieces. The disadvantage of this construction described above is that it is impossible to ensure a value for the distance between the poles greater than the tangential dimension of the magnet without reducing the radial dimension of the magnet. This results in a reduction of the density coefficient of the magnetic flux, i.e. a reduction of the effective magnetic flux in the gap.
It is also known to provide rotor with tangentially oriented magnets and pole pieces arranged between them, where the pole terminals are provided with little rims under which are placed T-clamps which tighten the rims and radially secure the magnet. The disadvantage of this construction is that an increase of the distance between the poles greater than the tangential dimension of the magnet results in a considerable magnetic dissipation flux in the gap between the poles, which hampers the commutation of the machine. The construction does not make it possible for the Longitudinal axes of the arcs of the pole pieces to alternate in position and thus form a broken line which is necessary for reducing the uneven rotation of the machine. The term pole piece arc as used herein means the curved portion of the pole piece farthest from the axis of the rotor.
It is also known to provide a rotor comprising modular packs, each consisting of pole pieces whose inside ends are founded in a sleeve of non-magnetic material and tangentially oriented permanent magnets mounted in semi-closed grooves formed by the pole pieces. The modular packs can be arranged in such a way as to make it possible for the longitudinal axes of the arcs of the pole pieces alternate in position to form broken lines. The shortcoming of this construction is that, in this case, the longitudinal axes of the magnets also alternate in position and form broken lines which leads to an increase of the dissipation flux of the magnets.